/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <windows.h>

#include "android-base/utf8.h"

#include <algorithm>
#include <string>


namespace android {
    namespace base {

// Helper to set errno based on GetLastError() after WideCharToMultiByte()/MultiByteToWideChar().
        static void SetErrnoFromLastError() {
            switch (GetLastError()) {
                case ERROR_NO_UNICODE_TRANSLATION:
                    errno = EILSEQ;
                    break;
                default:
                    errno = EINVAL;
                    break;
            }
        }

        bool WideToUTF8(const wchar_t *utf16, const size_t size, std::string *utf8) {
            utf8->clear();

            if (size == 0) {
                return true;
            }

            // TODO: Consider using std::wstring_convert once libcxx is supported on
            // Windows.

            // Only Vista or later has this flag that causes WideCharToMultiByte() to
            // return an error on invalid characters.
            const DWORD flags =
#if (WINVER >= 0x0600)
                    WC_ERR_INVALID_CHARS;
#else
                    0;
#endif

            const int chars_required = WideCharToMultiByte(CP_UTF8, flags, utf16, size,
                                                           NULL, 0, NULL, NULL);
            if (chars_required <= 0) {
                SetErrnoFromLastError();
                return false;
            }

            // This could potentially throw a std::bad_alloc exception.
            utf8->resize(chars_required);

            const int result = WideCharToMultiByte(CP_UTF8, flags, utf16, size,
                                                   &(*utf8)[0], chars_required, NULL,
                                                   NULL);
            if (result != chars_required) {
                SetErrnoFromLastError();
                CHECK_LE(result, chars_required) << "WideCharToMultiByte wrote " << result
                                                 << " chars to buffer of " << chars_required
                                                 << " chars";
                utf8->clear();
                return false;
            }

            return true;
        }

        bool WideToUTF8(const wchar_t *utf16, std::string *utf8) {
            // Compute string length of NULL-terminated string with wcslen().
            return WideToUTF8(utf16, wcslen(utf16), utf8);
        }

        bool WideToUTF8(const std::wstring &utf16, std::string *utf8) {
            // Use the stored length of the string which allows embedded NULL characters
            // to be converted.
            return WideToUTF8(utf16.c_str(), utf16.length(), utf8);
        }

// Internal helper function that takes MultiByteToWideChar() flags.
        static bool UTF8ToWideWithFlags(const char *utf8, const size_t size, std::wstring *utf16,
                                        const DWORD flags) {
            utf16->clear();

            if (size == 0) {
                return true;
            }

            // TODO: Consider using std::wstring_convert once libcxx is supported on
            // Windows.
            const int chars_required = MultiByteToWideChar(CP_UTF8, flags, utf8, size,
                                                           NULL, 0);
            if (chars_required <= 0) {
                SetErrnoFromLastError();
                return false;
            }

            // This could potentially throw a std::bad_alloc exception.
            utf16->resize(chars_required);

            const int result = MultiByteToWideChar(CP_UTF8, flags, utf8, size,
                                                   &(*utf16)[0], chars_required);
            if (result != chars_required) {
                SetErrnoFromLastError();
                CHECK_LE(result, chars_required) << "MultiByteToWideChar wrote " << result
                                                 << " chars to buffer of " << chars_required
                                                 << " chars";
                utf16->clear();
                return false;
            }

            return true;
        }

        bool UTF8ToWide(const char *utf8, const size_t size, std::wstring *utf16) {
            // If strictly interpreting as UTF-8 succeeds, return success.
            if (UTF8ToWideWithFlags(utf8, size, utf16, MB_ERR_INVALID_CHARS)) {
                return true;
            }

            const int saved_errno = errno;

            // Fallback to non-strict interpretation, allowing invalid characters and
            // converting as best as possible, and return false to signify a problem.
            (void) UTF8ToWideWithFlags(utf8, size, utf16, 0);
            errno = saved_errno;
            return false;
        }

        bool UTF8ToWide(const char *utf8, std::wstring *utf16) {
            // Compute string length of NULL-terminated string with strlen().
            return UTF8ToWide(utf8, strlen(utf8), utf16);
        }

        bool UTF8ToWide(const std::string &utf8, std::wstring *utf16) {
            // Use the stored length of the string which allows embedded NULL characters
            // to be converted.
            return UTF8ToWide(utf8.c_str(), utf8.length(), utf16);
        }

        static bool isDriveLetter(wchar_t c) {
            return (c >= L'a' && c <= L'z') || (c >= L'A' && c <= L'Z');
        }

        bool UTF8PathToWindowsLongPath(const char *utf8, std::wstring *utf16) {
            if (!UTF8ToWide(utf8, utf16)) {
                return false;
            }
            // Note: Although most Win32 File I/O API are limited to MAX_PATH (260
            //       characters), the CreateDirectory API is limited to 248 characters.
            if (utf16->length() >= 248) {
                // If path is of the form "x:\" or "x:/"
                if (isDriveLetter((*utf16)[0]) && (*utf16)[1] == L':' &&
                    ((*utf16)[2] == L'\\' || (*utf16)[2] == L'/')) {
                    // Append long path prefix, and make sure there are no unix-style
                    // separators to ensure a fully compliant Win32 long path string.
                    utf16->insert(0, LR"(\\?\)");
                    std::replace(utf16->begin(), utf16->end(), L'/', L'\\');
                }
            }
            return true;
        }

// Versions of standard library APIs that support UTF-8 strings.
        namespace utf8 {

            FILE *fopen(const char *name, const char *mode) {
                std::wstring name_utf16;
                if (!UTF8PathToWindowsLongPath(name, &name_utf16)) {
                    return nullptr;
                }

                std::wstring mode_utf16;
                if (!UTF8ToWide(mode, &mode_utf16)) {
                    return nullptr;
                }

                return _wfopen(name_utf16.c_str(), mode_utf16.c_str());
            }

            int mkdir(const char *name, mode_t mode) {
                std::wstring name_utf16;
                if (!UTF8PathToWindowsLongPath(name, &name_utf16)) {
                    return -1;
                }

                return _wmkdir(name_utf16.c_str());
            }

            int open(const char *name, int flags, ...) {
                std::wstring name_utf16;
                if (!UTF8PathToWindowsLongPath(name, &name_utf16)) {
                    return -1;
                }

                int mode = 0;
                if ((flags & O_CREAT) != 0) {
                    va_list args;
                    va_start(args, flags);
                    mode = va_arg(args, int);
                    va_end(args);
                }

                return _wopen(name_utf16.c_str(), flags, mode);
            }

            int unlink(const char *name) {
                std::wstring name_utf16;
                if (!UTF8PathToWindowsLongPath(name, &name_utf16)) {
                    return -1;
                }

                return _wunlink(name_utf16.c_str());
            }

        }  // namespace utf8
    }  // namespace base
}  // namespace android
